//-----------------------防(F5)按住刷新--------------------------
var seconds = 2;
var timerId = null;
function timer(){
	timerId = setTimeout("alert('刷新按钮(F5)不能按住超过'+seconds+'秒!');doLocation();",1000*seconds);
}
function doLocation(){
	top.window.location.reload();
}
function document.onkeyup(){
	clearTimeout(timerId);
}
function document.onkeydown(){
     if(window.event.keyCode == '116'){
     	timer();
        window.event.keyCode = 0;
        window.event.returnValue = false;
     }
}